PL120368B1 - Method of manufacture of thermal barrier in the form of cermet layer,on a substrate of superalloy on the basis of nickel or cobalteramicheskogo sloja-na posteli v sverkhsplave na bazise nikelja ili kobal'ta - Google Patents

Description

The subject of the invention is a method of producing a thermal barrier in the form of a metal-ceramic layer on a nickel-based or cobalt-based superalloy. Plasma sprayed metal-ceramic layers with the use of stabilized zirconium dioxide, forming a thermal protective barrier are known as MCrAlY alloys, where M stands for iron, nickel, cobalt, and mixtures of nickel and cobalt, and described in detail in U.S. Patent Nos. 3,542,530, 3,676,085, 3,754,903 and 3,928,026 relating to NiCoCrAlY alloy, and are widely used to protect metal parts exposed to high temperature. the task of lowering the temperature of the metal substrate and reducing the impact of transient thermal effects on structures. Such structures are commonly used in combustion chambers, transmission lines, afterburner lines of gas turbine engines, and can also be used to protect the surface of blades and lamellae. The most important feature of these layers is their thermal insulating ability, since the magnitude of lowering the temperature of the metal substrate and reducing the effects of transient thermal effects These properties are related to the low thermal conductivity of the oxide component and the thickness of its layer. to oxidative heat corrosion of the metal component, possibly close to the thermal expansion between the ceramic layer and the base alloy, adequate stabilization of the desired, crystalline structure, e.g. zirconium dioxide in In order to minimize the effects of non-linear thermal expansion caused by structural transformations, the possibility of damage occurring during manufacture and after operation. Several metal-ceramic coatings based on zirconium dioxide stabilized with magnesium oxide are known. Typically the substrate is a nickel or cobalt based superalloy such as Hastelloy X containing 0.1% by weight C, 0.5% Mn, 0.5% Si, 22% Cr, 1.5% Co, 9% Mo, 0.6 % W, 2 120 368 18.5% Fe and the remainder of Ni, which is covered with a nickel-5% aluminum or nickel-20% chromium bonding layer, an intermediate metal layer, a stabilized zirconium dioxide layer and an outer layer of stabilized zirconium dioxide. Such layers are plasma sprayed onto the substrate. It is now believed that this can be done more efficiently and at lower cost by introducing methods that result in a continuous increase in the concentration of zirconium dioxide from 0 at the interface between the sprayed layer and the substrate, to 100% on the outer surface of the sprayed layer. In general, coatings of approximately 380 µm are applied. The techniques used are detailed in U.S. Patent Nos. 3,006,782, 2,937,102, 3,091,548, and 3,522,064. Currently, one of the most readily used ceramic ingredients is zirconium dioxide, which can be used both by itself. and in mixtures with substances such as magnesium oxide, vanadium oxide, yttrium oxide, lanthanum oxide, cesium oxide, known as Tzirconium dioxide stabilizers in a more desirable, cubic crystal configuration. Accordingly, one of the best known protective agents for nickel-based cobalt-based superalloys against heat consists of a ceramic zirconium dioxide layer applied to a nickel-chromium or nickel-aluminum alloy substrate in which the concentration of the ceramic component increases or increases continuously or non-linearly with small jumps from the substrate to the outer layer. After these systems have been used and found to be working well, some defects have been observed. It has been found that they arise as a result of the oxygen degradation of the metal components followed by the peeling of the outer ceramic layer, while the removal of these defects is made difficult due to the resistance of the metal component to the action of acidic solutions that remove the coating layers. It has been found that the appropriate selection of the metal bonding coating significantly improves the functioning of the thermal barrier and, if necessary, enables the repair of the object. According to the invention, a method of producing a thermal barrier in the form of a metal-ceramic layer on a superalloy based on nickel or cobalt by applying a bonding metal coating to the substrate and applying a zirconium dioxide-based ceramic layer thereon or thereon, according to the invention, that the bonding coat is deposited from an alloy containing 15-40% chromium, 10-25 % aluminum, up to 1% yttrium, the remainder being a material selected from the group consisting of iron, cobalt, nickel and a mixture of nickel and cobalt, resulting in an unexpected increase in the thermal resistance of the barrier. Preferably, a bonding coating of an alloy containing 15-40% is applied. chromium, 10-25% aluminum, 0.01-1% yttrium with the remainder cobalt. It is obvious that although the layering is agly is more advantageous, but in the absence of adequate equipment for continuous spraying with a gradual increase in the zirconium dioxide content, one or more layers can be applied successively increasing each zirconium dioxide content. The zirconium dioxide in the layer forming the thermal barrier is stabilized in the system by the regular addition of calcium oxide or magnesium oxide. It may also contain other oxides such as yttrium oxide or lanthanum oxide, which are known to permanently stabilize zirconia in the cubic, or metastabilizers such as cesium trioxide. It is also possible to add anti-stabilizers such as nickel oxide, zinc oxide, cobalt oxide in admixtures with stabilized cubic zirconia in order to adjust the properties of the ceramic parts with respect to thermal shock resistance by selecting the compressive strength and thermal expansion coefficients according to the properties. metallic substrate. The term "zirconium dioxide ** as used below" means pure zirconium dioxide and includes ceramics based on zirconium dioxide with one or more of the admixtures given for example above. Example I. Plates of Hastelloy X alloy containing 0.1C by weight percent, 0.5Mn, 0.5Si, 22Cr, 1.5Co, 9Mo, 0.6W, 18.5Fe and the rest of Ni were covered with a known coating with the composition Ni-Cr and Z1O2, changing gradually and continuously, and the coating produced by the method according to the invention containing 67 , 5% Co, 20% Cr, 12% Al, 0.5% Y and 17% ZrO2 stabilized with magnesium oxide, in layers 0.022-0.035 cm thick 120368 3 Coatings are applied with a model 1068 plasma gun with a nozzle type 106F45H-1, in the model PS-61M plasmatron with a power of 40 kW, and two model 1008A powder feeders. One powder feeder contains the bond coating alloy, the other contains zirconium dioxide. Both feeders used argon overpressure. By changing the flow rate in the individual powder feeders, a continuous change in the concentration of the ceramic material in the coating of the thermal barrier is obtained. The granulation of the powder is not a critical parameter and the apparatus used used a powdered binder alloy with a granulation of 0.03-0.05 mm, considered the best. Using too fine granules caused clogging of the spray gun nozzle due to too rapid melting of the powder. A coating sample of known composition was subjected to a 100-hour and 200-hour static oxidation test at 1253K. Metallographic examination of the coating structure after the test showed that the nickel-chromium component was significantly oxidized after 100 hours. Another sample made in the same way was subjected to the oxidation test at the temperature of 1368K and then quenched in water. The metallographic examination of the coating structure after such a test showed almost complete oxidation of the nickel with cracks running vertically through the coating towards the metal substrate, while the metallographic examination of the coating samples according to the method according to the invention showed a much lower oxidation of the bonded coating, which indicates an extension of its life. The samples were also tested in a fluidized bed by subjecting them to the temperature of 1253K for 2 minutes and then cooling them for 2 minutes at room temperature. The test was stopped after 100 cycles and a satisfactory adhesion of the coating to the base alloy was found, and the metallographic test The alloy components were only partially oxidized, while the samples from the nickel-chromium alloy were completely oxidized under these conditions. Example II. The inner surfaces of several normal-sized combustion chambers of a Hastelloy X gas turbine engine, having the above grade, were covered with a continuously graded MgO (ZrO; rcobalt) chromium (aluminum) yttrium alloy of the above composition and subjected to engine testing. After a 150-hour endurance test, the tested alloy was much better in terms of edge resistance to crushing than conventional coatings with 17% MgO / Zr02 Ni-20% Cr, which covered another combustion chamber in the same test. Patent claims 1. Method for producing the barrier thermal in the form of a metal-ceramic layer on a nickel or cobalt-based superalloy substrate by applying a bonding metal coating to the substrate and applying a zirconium dioxide-based ceramic layer thereon or over it, characterized in that the bonding coat overlaps with an alloy containing 15-40% chromium, 10-25% aluminum, up to 1% yttrium, the rest being a material selected from the group consisting of iron, cobalt, nickel and mixtures of nickel and cobalt. 2. The method according to claim The method of claim 1, wherein the bond coating is made of an alloy containing preferably 15-40% chromium, 10-25% aluminum, 0.01-1% yttrium, the balance being cobalt. PL

Claims (2)

Claims 1. A method of producing a thermal barrier in the form of a metal-ceramic layer on a nickel-based or cobalt-based superalloy substrate by applying a bonding metal coating to the substrate and applying a ceramic layer based on zirconium dioxide to the substrate or thereto, characterized by that the bonding coating is composed of an alloy containing 15-40% chromium, 10-25% aluminum, up to 1% yttrium, the remainder being a material selected from the group consisting of iron, cobalt, nickel and a mixture of nickel and cobalt. 2. The method according to claim The method of claim 1, wherein the bond coating is made of an alloy containing preferably 15-40% chromium, 10-25% aluminum, 0.01-1% yttrium, the balance being cobalt. PL